Known in the art are processes for the production of ammonium carbonates which comprise interaction of gaseous ammonia and carbon dioxide in the presence of water, both as vapours and liquid (cf. German Pat. Nos. 237,524 and 448,758).
Depending on proportions between the reacting gases, salts of various compositions and mixtures thereof can be obtained (cf. E. Janecke, Zietsrift fur Electrochemie, 35, 716/1926/).
______________________________________ Content, % by mass, of Salt Formula M.W. NH.sub.3 CO.sub.2 H.sub.2 O 1 2 3 4 5 6 ______________________________________ Ammo- nium bi- car- bonate NH.sub.4 HCO.sub.3 79 21.54 55.66 22.8 Ammo- nium car- bonate (NH.sub.4).sub.2 CO.sub.3 96 35.45 45.80 18.75 Ammo- nium car- bonate mono- hydrate (NH.sub.4).sub.2 CO.sub.3 . H.sub.2 O 114 29.85 38.56 31.58 Ammo- nium car- bamate NH.sub.4 COONH.sub.2 78 43.63 56.37 0 Ammo- nium car- bamate mono- hydrate NH.sub.4 COONH.sub.2 . H.sub.2 O 96 35.45 45.80 18.75 Ammo- nium bicar- bonate- mono- 2NH.sub.4 HCO.sub.3 (NH.sub.4).sub.2 -- hydrate CO.sub.3 . H.sub.2 O 272 25.02 48.50 26.48 Ammo- nium bicar- bonate- carba- mate NH.sub.4 HCO.sub.3 NH.sub.4 COONH.sub.2 157 32.52 56.02 11.46 ______________________________________
The desired product produced by the above-described processes is formed on the reactor surfaces, through which the heat evolved during the reaction is removed, in the form of a solid monolithic layer, thus substantially hindering discharging of the product.
Also known is a continuous process for the production of ammonium carbonates from liquid ammonia, carbon dioxide and water vapours, wherein the desired product is formed within the reactor working space in the form of fine particles which fall to the reactor bottom and are discharged by means of a screw conveyor. (Cf. USSR Inventor's Certificate No. 220246).
The process is conducted at the temperature of 10.degree. C. under the pressure of 80 mm Hg. The reactor walls do not participate in the heat removal and the product is not formed thereon, since the heat evolved in the reaction is compensated by evaporation and expansion of liquid ammonia.
However, to maintain the temperature in the reactor at 10.degree. C., it is necessary to have substantially 2-time excess of ammonia and continuous evacuation from the reactor. The product yield based on ammonia is about 50%, while for a total utilization of ammonia additional purification thereof from carbon dioxide and liquefaction are required which are additional steps complicating the process.
Preparation of ammonium carbamate from liquid ammonia and liquid carbon dioxide (cf. FRG Pat. No. 1,097,430) by bulk condensation is carried out in an excess of carbon dioxide, full utilization whereof for increasing the desired product yield is only possible after purification from ammonia and liquiefaction which again hinders the process.